In general, the operations performed by the human hands can be broadly classified based on a control viewpoint and an implementation viewpoint. From the control viewpoint, the human hand operation is divided into a tip grasping operation in which a human grasps an object using his or her finger tips, such as grasping a pen in one hand to write, a whole or power grasping operation in which the human grasps an object using his or her whole palm or all fingers, and an operation in which the human maintains a state of being in contact with an object without grasping it such as pushing it.
From the implementation viewpoint, the human hand operation is divided into an operation in which a human hand acts as a medium of transmitting a force to an object, such as grasping and turning a doorknob, grasping and pivoting about a horizontal bar, or pushing a heavy object, a pick and move operation in which the human picks up and moves an object, such as picking up a cup or beaker and transferring it to another place, moving a keychain or the like with a finger hooked on it, or sweeping coins or the like in a hand, and a precise task in which the human uses his or her hands precisely, such as grasping a pen in one hand to write or draw, or manipulating a complicated Rubik's cube or the like.
The human hands have a considerably complicated structure that consists of a plurality of joints, and bones and muscles for moving the joints. In addition, the human hands are surrounded by sensitive nervous tissues that can sense haptic sensation, temperature, pressure, and the like. Both hands of the human are composed of 54 bones, which correspond to 25% of a total of 206 bones in the human body. Moreover, the human hands include so extremely complicated tissues as to control 30% of regions that take charge of the motor nerves of a brain.
Besides, in the case where the human performs a manual operation, various items of information acquired from the internal sensors of the human hands and the external sensors like the human eyes are directly feedback to the brain, which in turns correctly analyzes the sensor information items and determines the current status based on the currently inputted sensor information as well as empirical knowledge accumulated in the growth process in the past.
The human brain can perform, in real-time, a multiple-path planning regarding how to operate 54 bones based on the analyzed sensor information, and can calculate a multi-control input for a muscular force and a degree of motion of muscles needed to perform the multiple-path planning so that the human can excellently perform a variety of types of manual operations in association with the functions such as determination, storage and calculation of the brain
A conventional robot hand, which is a human-like robot hand that creates a robotic imitation of the human hand, is developed and manufactured. Such a conventional robot hand, however, entails a problem in that a driver such as a motor or a pump and a sensor is relatively difficult to install in terms of space efficiency and balance as compared to the installation of the human hands as mentioned above, in that the performance of the driver or the sensor itself is greatly degraded as compared to that of the human, and in that it is substantially impossible to analyze and process information acquired through the sensor to simultaneously control about 20 joints using a proper force and path.
Despite the above-mentioned problem, the human-like robot hand is aimed at replacing all the operations performed by the human, so that although the robot hand itself has a complex shape, it does not perform various operations other than a basic operation of manipulating an object having a predetermined specific shape. In addition, the conventional robot hand is advantageous in that the rate of success of a repeated operation is low even in some executable operations and stability of gripping force, transmission and formation is poor, which makes it difficult to be put into practical use.
Since the development of a robot hand structure that imitates the human hand as it is requires a long-term approach, there is a need for the development of a robot hand for exclusive purpose of performing a specific work, which can reliably and stably perform even some limited operations but not all the operations performed by the human to promote commercialization of the robot.